During cardiac surgery, a heart-lung machine is utilized. The heart-lung machine is used by being embedded in an extracorporeal circulation circuit and performs oxygenation of blood drained from a patient, and filtering for elimination of foreign bodies, and the like. There are various types of heart-lung machines (also known as perfusion systems) depending on differences such as the type of gas exchange unit, the type of pump, the position arrangement of pump, and the like. However, a heart-lung machine generally includes a reservoir (for venous blood), an oxygenator, a heat exchanger, a pump, and a plurality of tubes for connecting the components (for example, refer to JP-A-2009-160265).
One type of pump adapted for use in the heart-lung machine is a centrifugal pump which delivers blood by utilizing centrifugal force occurring due to rotations of an impeller. Generally, the centrifugal pump includes a housing, wherein the impeller is rotatably disposed inside the housing by a shaft which is provided at the center rotational axis of the impeller. A bearing on the housing rotatably supports the shaft. In order to reduce the occurrence of a thrombus (blood clot), a centrifugal pump may be used in which the bearing is formed as a pivot bearing.
In a case of the centrifugal pump employing the pivot bearing, however, the occurrence of hemolysis (damage to blood corpuscles) may become more likely due to sliding between the shaft and the pivot bearing. In addition, a thrombus may be formed on a sliding surface between the shaft and the pivot bearing. In a case where a thrombus is formed, there is a possibility of causing resistance against rotations of the impeller.